Fat continuous food products are well known in the art and include for example shortenings comprising a fat phase and water in oil spreads like margarine comprising a fat phase and an aqueous phase.
The fat phase of margarine and similar edible fat continuous spreads is often a mixture of liquid oil (i.e. fat that is liquid at ambient temperature) and fat which is solid at ambient temperatures. The solid fat, also called structuring fat or hardstock fat, serves to structure the fat phase (being the case in for example a shortening as well as in a water in oil emulsion) and helps to stabilize the aqueous phase, if present, by forming a fat crystal network. For a margarine or spread, ideally the structuring fat has such properties that it melts or dissolves at mouth temperature. Otherwise the product may have a heavy and/or waxy mouthfeel.
Margarine is generally defined as a composition containing at least 80 wt % fat and about 20 wt % aqueous phase. In contrast, emulsions containing less than 80 wt % fat are generally called spreads. Nowadays the terms margarine and spread are sometimes used interchangeably although in some countries the commercial use of the term margarine is subject to certain regulatory requirements. The difference between margarine and spread is mainly the amount of fat. Therefore, for the purpose of the present invention the terms margarine and spread will be used interchangeably.
Margarine may be used for different applications including spreading, (shallow) frying and baking. In the market place margarine is generally sold as one of three principal types, namely hard or stick margarine (generally referred to as wrapper margarine), soft or tub margarine and liquid or pourable margarine. Wrapper margarine would typically have a Stevens hardness value of more than 140 gram at 5 degrees Celsius and more than 50 gram at 20 degrees Celsius. Tub margarine would typically have a Stevens hardness value of 20 to 140 gram at 5 degrees Celsius and 10 to 20 gram at 20 degrees Celsius. The Stevens hardness value is the value as measured according to the method described in the experimental section. Liquid margarine would typically have a Bostwick value of at least 4 at 15° C., preferably a Bostwick value of at least 7. The Bostwick value is the value as measured according to the method described in the experimental section.
Wrapper margarine needs to have a certain firmness (also called hardness) to keep its shape preferably also at higher temperatures. It should also be able to withstand a certain amount of pressure to enable stacking of the wrapper margarine like e.g. at the manufacturing site, during transport, storage or presentation in a shop.
To achieve the required amount of firmness in a wrapper margarine (expressed as Stevens hardness value) the choice of fats that can practically be used as structuring fat is rather limited. If the melting point of the structuring agent is too high the melting properties in the mouth are unsatisfactory. If on the other hand, the melting point is too low, the emulsion stability will be negatively affected.
A wrapper margarine thus needs to be rather firm. This usually requires a relatively high amount of saturated fatty acid (SAFA) in the structuring fat. However, some consumers prefer wrapper margarines that are low in SAFA and preferably have a good nutritional profile (by providing for example essential fatty acids like omega-3 and omega-6).
Trans unsaturated fatty acids are known to have a good structuring capacity and sometimes are used in addition or instead of SAFA to impart the required structure in a wrapper margarine. However, some experts have called for reductions in these fatty acids to improve cardiovascular health.
Triacylglycerols (TAG) are the major constituents of natural fats and oils and are esters of glycerol and fatty acids. The chemical structure of the fatty acid and the distribution of the fatty acids over the glycerol backbone determine (at least partly) the physical properties of a fat. The physical properties of fats, like for example the solid fat content (SFC) expressed as N-value, can be modified by altering the chemical structure of the fat. Well known techniques that are widely used include hydrogenation and interesterification.
Hydrogenation alters the degree of unsaturation of the fatty acids and as such alters the fatty acid composition. This allows e.g. plastic fats to be made from liquid oils. A draw back of hydrogenation, especially of partial hydrogenation, is the formation of by products like e.g. trans unsaturated fatty acids. Furthermore additional process steps are required and some consumers perceive a chemical process such as hydrogenation as undesirable.
Interesterification retains the fatty acid composition but alters the distribution of the fatty acids over the glycerol backbones. Interesterification can be done chemically or with the aid of enzymes. Usually a mixture of two different fats, that by themselves are not or less suitable as a structuring fat, is subjected to interesterification. The resulting interesterified fat will have improved structuring properties compared to the starting materials. A draw back of interesterification may be the formation of by products like e.g. free fatty acids and diglycerides. Also enzymatic interesterification introduces additional process steps which may be complicated and introduce additional costs. Furthermore some consumers perceive chemically modified fats as unnatural and therefore undesirable.
U.S. Pat. No. 4,341,813 concerns stick and pat margarines wherein the blend of vegetable oil and hard stock is high in polyunsaturates and has a low-trans-isomer fatty acid content. The fat blend comprises hydrogenated and interesterified fat.
EP 0 041 299 relates to natural fat blends which can be used for producing margarines which are packaged in wrappers. The fat blend is substantially free of hydrogenated and interesterified fats. The fat blends contain more than 35 wt % SAFA on total fat.
GB 2 292 949 relates to stick-type margarines and other spreads which contain no detectable levels of trans fatty acids or tropical oils and comprise specific blends of co-interesterified liquid unsaturated vegetable oils hardstocks.
When lowering the amount of SAFA (while keeping the fat essentially free of hydrogenated fat) in a wrapper margarine, softer and/or less (temperature) stable products could not be avoided up to now.